1. Technical Field
The present invention relates to a technique for identifying a document size on the basis of a measured intensity of light.
2. Related Art
Conventionally known is a technique for identifying a document size of a document being scanned on the basis of the intensity of light received by a one-dimensional image sensor (for example, Japanese Laid-open Patent Publication 2007-28185). In Japanese Laid-open Patent Publication 2007-28185, the amount of change in the intensity of light received at the one-dimensional image sensor is acquired until a state where a document cover is open changes to a state where the document cover is closed, and the document is determined not to be present at a position where this amount of change does not exceed a threshold value and the document is determined to be present at a position where the amount of change does exceed the threshold value. The length of the document is identified in the direction of the one-dimensional image sensor by determining whether or not the document is present in this manner for each of the positions of the one-dimensional image sensor.
However, in a case where ambient light is incident at an angle close to parallel to a document platen, then the intensity of the light received by the one-dimensional image sensor does not change significantly even when the document cover is closed. As such, a problem has emerged in that the document size is wrong.